Hyponatremia in a Patient With Cancer

Simultaneous Presentation of Secondary Adrenal Insufficiency and Primary Hypothyroidism due to Pembrolizumab: A Case Report

Checkpoint inhibitors have gained increased traction in recent years as they have improved prognosis in various malignancies. Pembrolizumab, an anti-programmed cell death protein (PD-1) monoclonal antibody, has become a first-line chemotherapeutic agent for stage II non-small cell lung cancer since 2019. Although much more common with nivolumab, several immune-related adverse effects, particularly endocrinopathies, have been linked with pembrolizumab. We describe a case of a 59-year-old man with a history of unspecified lung cancer who presented with severe hyponatremia later attributed to secondary adrenal insufficiency and accompanying primary hypothyroidism secondary to pembrolizumab. Diagnosing adrenal insufficiency in patients on immune checkpoint inhibitors like pembrolizumab can be challenging due to nonspecific symptoms, making it crucial to rule out other causes of hyponatremia. Immunotherapy is known to cause thyroid immune-related adverse events, and anti-thyroid antibodies may not always be present in the diagnosis of hypothyroidism. Although there are some reported cases of pembrolizumab-induced adrenal insufficiency, the link between immunotherapy and endocrine disorders remains unclear. To our knowledge, no case reports exist that describe both primary hypothyroidism and secondary adrenal insufficiency after taking pembrolizumab, although such cases have been documented with axitinib. Timely diagnosis and treatment of adrenal insufficiency is crucial to prevent adverse effects, especially in patients with cancer receiving immunotherapy, as highlighted in this case.

Immune checkpoint inhibitors and kidney disease

PURPOSE OF REVIEW

Immune checkpoint inhibitors (ICIs) have changed the landscape of cancer treatment. However, use of ICIs can be limited by inflammatory toxicities referred to as immune-related adverse events (irAEs). ICI-associated acute kidney injury (ICI-associated AKI) affects 3-5% of ICI users.

RECENT FINDINGS

With the rapidly growing indication of ICI, knowledge of ICI-associated kidney toxicity has also expanded from case series to large multicentre cohort studies. In this review, we discuss the clinical features, risk factors, clinicopathological correlations and prognosis of ICI-associated AKI from the most recent rigorously conducted retrospective cohort studies. We also discuss recent advances in diagnostic biomarker investigation, treatment and the unique challenge faced in the kidney transplant population.

SUMMARY

With more comprehensive understanding of the clinical features and risk factors, ICI-associated AKI is commonly diagnosed clinically, especially given the inherent challenges performing a kidney biopsy in the cancer population; however, this highlights the urgent need for improved noninvasive diagnostic biomarkers to aid diagnosis and prognosis. Prospective studies are needed to better define the optimal treatment of ICI-associated AKI and to minimize the risk of graft loss in patients with kidney transplant who require ICIs.

Sodium and Potassium Dysregulation in the Patient With Cancer

Sodium and potassium disorders are pervasive in patients with cancer. The causes of these abnormalities are wide-ranging, are often primary or second-order consequences of the underlying cancer, and have prognostic implications. The approach to hyponatremia should focus on cancer-related etiologies, such as syndrome of inappropriate antidiuretic hormone, to the exclusion of other causes. Hypernatremia in non-iatrogenic forms is generally due to water loss rather than excessive sodium intake. Debilitated or dependent patients with cancer are particularly vulnerable to hypernatremia. Hypokalemia can occur in patients with cancer due to gastrointestinal disturbances, resulting from decreased intake or increased losses. Renal losses can occur as a result of excessive mineralocorticoid secretion or therapy-related nephrotoxicity. The approach to hyperkalemia should be informed by historical and laboratory clues, and pseudohyperkalemia is particularly common in patients with hematological cancers. Hyperkalemia can be seen in primary or metastatic disease that interrupts the adrenal axis. It can also develop as a consequence of immunotherapy, which can cause adrenalitis or hypophysitis. Tumor lysis syndrome (TLS) is defined by the development of hyperkalemia and is a medical emergency. Awareness of the electrolyte abnormalities that can befall patients with cancer is vital for its prompt recognition and management.

Electrolyte and Acid-Base Disorders associated with Cancer Immunotherapy

Novel immunotherapy drugs have changed the landscape of cancer medicine. Immune checkpoint inhibitors and chimeric antigen receptor T cells are being used and investigated in almost all solid cancers. Immune-related adverse events have been associated with immunotherapies. Acute kidney injury has been the most commonly associated kidney adverse event. In this review, we showcase the several associated electrolyte disorders seen with immunotherapy. Immune checkpoint inhibitors can lead to hyponatremia by several mechanisms, with the syndrome of inappropriate antidiuresis being the most common. Endocrine causes of hyponatremia are rare. Hypokalemia is not uncommon and is associated with both proximal and distal renal tubular acidosis. Hypercalcemia associated with immune checkpoint inhibitors has led to some interesting observations including immune checkpoint inhibitor-induced parathyroid hormone - related peptide production, sarcoid-like granulomas, and hyper-progression of the disease. Hypocalcemia and hyperphosphatemia may be seen with immune checkpoint inhibitor-induced tumor lysis syndrome. Chimeric antigen receptor T cell therapy-associated electrolyte disorders are also common. This is associated chiefly with hyponatremia, although other electrolyte abnormalities can occur. Early recognition and prompt diagnosis may help providers manage the mechanistically varied and novel electrolyte disorders associated with immunotherapy.

Kidney toxicity of the BRAF-kinase inhibitor vemurafenib is driven by off-target ferrochelatase inhibition

A multitude of disease and therapy related factors drive the frequent development of kidney disorders in cancer patients. Along with chemotherapy, the newer targeted therapeutics can also cause kidney dysfunction through on and off-target mechanisms. Interestingly, among the small molecule inhibitors approved for the treatment of cancers that harbor BRAF-kinase activating mutations, vemurafenib can trigger tubular damage and acute kidney injury. BRAF is a proto-oncogene involved in cell growth. To investigate the underlying mechanisms, we developed cell culture and mouse models of vemurafenib kidney toxicity. At clinically relevant concentrations vemurafenib induces cell-death in transformed and primary mouse and human kidney tubular epithelial cells. In mice, two weeks of daily vemurafenib treatment causes moderate acute kidney injury with histopathological characteristics of kidney tubular epithelial cells injury. Importantly, kidney tubular epithelial cell-specific BRAF gene deletion did not influence kidney function under normal conditions or alter the severity of vemurafenib-associated kidney impairment. Instead, we found that inhibition of ferrochelatase, an enzyme involved in heme biosynthesis contributes to vemurafenib kidney toxicity. Ferrochelatase overexpression protected kidney tubular epithelial cells and conversely ferrochelatase knockdown increased the sensitivity to vemurafenib-induced kidney toxicity. Thus, our studies suggest that vemurafenib-associated kidney tubular epithelial cell dysfunction and kidney toxicity is BRAF-independent and caused, in part, by off-target ferrochelatase inhibition.